1. Field of the Invention
The present invention relates to an ejector valve for a product sorter.
2. Description of Prior Art
Certain product sorters use an ejector to separate the unacceptable product (objects) from that which is acceptable. A stream of product such as diamonds, coffee beans, grain or peanuts passes by the nozzle of the ejector, usually one at a time. If the product is acceptable, individual ones of the product pass by the ejector unhindered. If individual ones of the product are unacceptable, the ejector discharges a burst of air which alters the path of the unacceptable product, thereby rejecting them. Conversely a desired product may be ejected while undesired product flows unhindered. The ejector apparatus includes a pressurized chamber, a nozzle and a solenoid valve separating the pressurized chamber from the nozzle.
Valves of the prior art contain a movable disk or a valve flap made of a flexible material fastened at one end. When the solenoid is not activated, the flexible flap rests against a valve seal, thereby blocking an aperture between the high pressure chamber and the nozzle. In closed position air is not communicated from the pressurized chamber into the nozzle, and acceptable product is allowed to pass by the nozzle unhindered.
When the solenoid is activated, the unfastened end of the flexible flap is magnetically pulled off the valve seal, allowing air to flow from the high pressure chamber through the aperture and through the nozzle. In this open position, air flowing out of the nozzle blows any unacceptable product passing in front of the nozzle to divert its path. The solenoid is then deactivated to re-close the valve so that acceptable product again passes by the ejector nozzle unhindered. The valve typically opens and closes quickly during product sorting, flexing the valve flap each time. The valve flap may eventually wear out and break, shutting down the entire sorter until the ejector is replaced or repaired.
In another prior art mechanism a disk which is not fastened, but is constrained, to slide between open and closed positions. The valve is closed when the solenoid is not activated and the valve disc rests upon the valve seat which blocks the aperture between the high pressure chamber and the nozzle. Air does not flow out of the nozzle when the valve is closed so that acceptable product passing in front of the nozzle falls unhindered. The valve is open when the solenoid is activated so that the valve disc slides towards the solenoid and away from the valve seat, allowing air to flow from the pressurized chamber through the valve aperture and through the nozzle to reject the product. The solenoid valve is then deactivated so that the valve disc slides back onto the seal thereby blocking the aperture and re-closing the valve. In prior art solenoid valves in which air is injected to one side of the solenoid, the resulting uneven air flow and distribution can cause a valve disc to move in its chamber in an inclined, non-parallel manner.
The activation current through the coil of the solenoid causes the coil to heat up during operation. In certain prior art valves, the coil is located within the air chamber so that the air flows around the coil to keep it cool. The air flow around the coil is often insufficient to cool it and often cools only a part of the coil. In certain prior art devices a cushion is disposed at one end of the solenoid so that the solenoid is held tight against part of the valve seat body. This cushion prevents air from flowing through the solenoid coil. The space around the coil that holds the cooling air also serves as an air reservoir that must be filled with air under pressure prior to the exit of air from the solenoid. This reservoir coupled with another air holding space beneath the disk creates a relatively large air volume that must be traversed by the pressurized air that is to knock out an unwanted object. Due to the relatively large volume, an undesirable amount of time is required for a knock-out air burst. Such an extended burst may eject a desired object as well as others that were not intended to be ejected.
With both the prior art flap valves and disk valves, uneven air flow and/or uneven flap or disc movement can require more time to eject a particular object.
Typical prior art sorting machines are shown in U.S. Pat. Nos. 3,028,960; 3,914,601; 4,057,146; 4,699,274; 4,513,868; 4,697,709 and 4,454,029 (both commonly owned With the present invention); and U.K. patent application 2,136,957A.